What are the main instructions and components used when creating a Dockerfile?

Main instructions and components of a Dockerfile:

• FROM — base image from which the new image is inherited.
• RUN — execute commands in the container during build (e.g., installing packages).
• COPY and ADD — copy files from the build context into the image.
• CMD — command that runs when the container starts (can be overridden).
• ENTRYPOINT — sets the main executable of the container.
• WORKDIR — sets the working directory inside the container.
• ENV — sets environment variables.
• EXPOSE — declares ports that the container listens on.
• VOLUME — declares mount points for data storage.

Example Dockerfile:

FROM openjdk:11
WORKDIR /app
COPY . /app
RUN ./gradlew build
EXPOSE 8080
CMD ["java", "-jar", "build/libs/app.jar"]